This section provides background information related to the present disclosure which is not necessarily prior art.
For energy-efficient operation of such electrical enclosure cooling devices, it is necessary to select at any operating point that coolant circuit from the two coolant circuits that can provide the required cooling power more efficiently. This requires one the one hand, knowledge of the required cooling power, that is, the cooling power needed to keep the internal electrical enclosure temperature at a target temperature. On the other hand, the efficiency or a representative energy efficiency value the respective coolant circuit has when it is to provide the currently required cooling power must be determined at the respective operating point.
In electrical enclosure cooling devices known from prior art, which are, for example, solely based on the principle of the refrigerating machine, and where the required cooling power and energy efficiency of the refrigerating machine are unknown, it is common to run the refrigerating machine at a predetermined speed regardless of the actual required cooling power, for example, at the maximum speed of the compressor, at which the refrigerating machine is expected to have its highest mean efficiency over its component life. Furthermore, operating the compressor at its maximum speed ensures that spikes in required cooling power can be compensated. Conversely, operating the refrigerating machine at a high compressor power output entails that the refrigerating machine must be run in a cycle operation in which the internal electrical enclosure temperature performs a hysteresis between an upper and lower threshold temperature around the target temperature. This has energy disadvantages, particularly compared to the ideal situation in which the refrigerating machine provides a cooling power that matches the required cooling power more or less accurately.